CT perfusion in ischaemic stroke has become established in most centres with stroke services as an important adjunct, along with CT angiography (CTA), to conventional unenhanced CT brain imaging.
It enables differentiation of salvageable ischaemic brain tissue (the penumbra) from irrevocably d...
Below is an approach used for the "primary survey" of a CT polytrauma/multitrauma (also called trauma CT or whole body CT), often performed at the CT console with the patient still on the CT table. It allows rapid communication of significant findings to the trauma team as well as the decision ...
This is a basic article for medical students and other non-radiologists
Chest x-ray CVC (central venous catheter) position should be assessed following initial placement and on subsequent radiographs.
This is a summary article; for a more in-depth reference article see centr...
Cystography is a fluoroscopic study that images the bladder. It is similar to a voiding cystourethrogram (VCUG), and the difference between the studies is primarily one of emphasis; a cystogram focuses on the bladder and a VCUG focuses on the posterior urethra. The study has been adapted to CT w...
Deductive echocardiography is a step-by-step approach in diagnosing and differentiating congenital heart disease.
position of heart
Deep brain ultrasound (DBUS) therapy is a form of precision medicine using a technique based on the principle of high-intensity focused ultrasound (HIFU), also referred to as focused ultrasound surgery (FUS).
The method combines two main components 1:
MRI of the ...
The deepest (maximal) vertical pocket (DVP) depth is considered a reliable method for assessing amniotic fluid volume on ultrasound 1-2. It is performed by assessing a pocket of maximal depth of amniotic fluid which is free of umbilical cord and fetal parts.
The usually accepted values are:
Densitometric vertebral fracture assessment (VFA) is an image of the lumbar and thoracic spine acquired on dual energy x-ray absorptiometry (DXA) scanners, for the purpose of diagnosing osteoporotic vertebral fractures.
The technique is available on DXA scanners under a variety of...
The Denver criteria are a set of screening criteria for blunt cerebrovascular injury (BCVI) in trauma used to reduce the need for CT angiography and its associated radiation exposure.
The screening protocol criteria 1,3 for BCVI are divided into signs and symptoms of BCVI a...
Describing a fracture is a basic requirement when making an assessment of a plain radiograph. There are many ways to approach the assessment of the radiograph; this is just one approach.
I: Describe the film
What film (or films) are you looking at? Check the who, what, why, when, and where.
Atrial situs refers to the relative position of the cardiac atria in relation to abdominal viscera and the midline.
Identification of atrial situs is an important initial step in the antenatal and postnatal diagnosis of cardiac structural and situs anomalies.
Diffuse pulmonary nodules are usually seen as multiple pulmonary nodular opacifications on a HRCT chest scan. They can signify disease processes affecting either the interstitium or the airspace. They can range from a few millimetres to up to 1 cm and when very small and numerous there can be so...
A number of differentials must be kept in mind while approaching diffuse pulmonary nodules. Interpretation is easier if nodules are the only abnormality.
These differentials can be narrowed down based on the several criteria:
Based on appearance
The digastric (or biventer) line has been described and used to evaluate basilar invagination on frontal skull plain film and coronal recontructed CT image.
The digastric line is drawn between right and left digastric grooves. The tip of the odontoid process and atlanto-occipital joint normall...
Dolan's lines are the collective name given to three lines described by Dolan and Jacoby 1 that aid in evaluating for maxillofacial fractures on an occipitomental skull radiograph. They are usually used as an adjunct to McGrigor-Campbell lines.
orbital line traces the inner margins of the later...
This is a basic article for medical students and other non-radiologists
Elbow radiographs are common plain films that are obtained frequently in the emergency department.
anterior humeral line
drawn down the anterior surface of the humerus
should intersect the mi...
Distinguishing between an empyema and a peripherally located pulmonary abscess is essential.
Lung abscesses are usually managed with prolonged antibiotics and physiotherapy with postural drainage whereas an empyema usually requires percutaneous or surgical drainage.
Distinguishing between enchondromas and low-grade conventional chondrosarcomas is a frequent difficulty as the lesions are both histologically and radiographically very similar.
It is important to remember, though, that differentiating between them may be a moot point since both can either be c...
Getting a film with endometrial polyp in the exam is one of the many exam set-pieces that can be prepared for.
Transabdominal and transvaginal pelvic ultrasound images in a lady with post-menopausal bleeding show an anteverted uterus with focal increased endometrial thickness to 1...
Enlargement of the cardiac silhouette on a frontal (or PA) chest x-ray can be due to a number of causes 1:
cardiomegaly (most common cause by far)
anterior mediastinal mass
prominent epicardial fat pad
AP projection (from supine radiographs taken ...
Enteroclysis is a gastrointestinal technique designed to provide improved evaluation of the small bowel. The conventional fluoroscopic technique is not widely used since it is somewhat invasive, time and labour intensive, and not particularly pleasant for the patient. The exam also requires a de...
Epistaxis (nosebleed) is very common and has a broad differential diagnosis in clinical practice. In clinical practice, anterior epistaxis are mainly located in Kiesselbach's plexus and posterior epistaxis (5% of all epistaxis) in Woodruff's plexus.
Epistaxis is very common, with ...
Errors in diagnostic radiology occur for a variety of reasons related to human error, technical factors and system faults.
This classification was proposed by Renfrew et al. 5 in 1992, and at the time of writing (July 2016) remains the most widely accept...
Evacuation proctography (defecography) is a fluoroscopic technique to evaluate pelvic floor disorders. The technique traditionally involves fluoroscopy and barium, but an analogous MRI technique has also been developed (see: MR defaecating proctography).
incomplete or obstructed de...
Recurrent bone tumours are a common complication post curettage or resection.
Radiographs taken pre- and postoperatively are sufficient for evaluation of recurrence based on the following features:
matrix mineralisation (characterist...
Exam set-pieces refer to those cases that can be considered likely to turn up in the exam setting and can be prepared for. In the oral exam, having a prepared "speech" for these set-pieces allows the candidate to focus less on the stress of describing what is in front of them and more on conside...
Expiratory HRCT is an useful method for detecting small airway obstructive disease in which the air remain trapped in the small airways even after the expiration and appear as mosaic attenuation.
Ideally, an expiratory HRCT scan should be performed in all obstructive airway diseases...
Differentiating extradural (EDH) from subdural (SDH) haemorrhage in the head is usually straightforward, but occasionally it can be challenging. SDHs are more common and there are a few distinguishing features which are usually reliable.
History and mechanism of injury
Fetal femur length (FL) is one of the basic biometric parameters used to assess fetal size. Femur length together with biparietal diameter, head circumference, and abdominal circumference are computed to produce an estimate of fetal weight. In the second trimester this may be extrapolated to an ...
Abdominal circumference (AC) is one of the basic biometric parameters used to assess fetal size. AC together with biparietal diameter, head circumference, and femur length are computed to produce an estimate of fetal weight. In the second trimester this may be extrapolated to an estimate of gest...
Fetal cardiothoracic (C/T) circumference ratio is a parameter than can be used in assessment of fetal cardiac and thoracic/chest wall anomalies. It is the ratio of the cardiac circumference to the thoracic circumference and may be easily measured on fetal ultrasound/echocardiography.
Fetal MCA systolic/diastolic (S/D) ratio is an important parameter in fetal middle cerebral arterial Doppler assessment. It is a useful predictor of fetal distress and intrauterine growth restriction (IUGR).
During pregnancy the middle cerebral (and other intracranial)...
Fetal middle cerebral arterial (MCA) Doppler assessment is an important part of assessing fetal cardiovascular distress, fetal anaemia or fetal hypoxia. In the appropriate situation it is a very useful adjunct to umbilical artery Doppler assessment. It is also used in the additional work up of:
The fetal middle cerebral arterial (MCA) peak systolic velocity (PSV) is an important parameter in fetal MCA Doppler assessment.
The fetal MCA should be sampled~2 mm from the origin of the fetal internal carotid artery and the angle of the ultrasound beam and the directi...
The fetal middle cerebral artery (MCA) pulsatility index (PI) is a key parameter used in fetal middle cerebral arterial Doppler assessment. It is calculated by subtracting the end diastolic velocity (EDV) from the peak systolic velocity (PSV) and then dividing by the time averaged (mean) velocit...
The first metatarsal axis is represented by a line drawn down the longitudinal axis of the shaft of the first metatarsal. It can be drawn on lateral and DP radiographs and is used to measure the:
first metatarsal inclination angle
talo-first metatarsal angle
Flattening of the diaphragm is the most sensitive sign on chest radiographs for the presence of hyperinflation of the lungs, usually due to emphysema 1-2.
The normal dome of each hemidiaphragm should rise at least 1.5 cm above a line connecting the costophrenic angle posteriorly and sternophren...
The Fleischner society pulmonary nodule recommendations are for the follow-up and management of pulmonary nodules smaller than 8 mm detected incidentally in patients >35 years on non-screening CT. The initial guidelines for the management of solid nodules were released in 2005 1, and guidelines...
Fluid-fluid levels in bone tumours is a commonly encountered finding, both in benign as well as malignant bone tumours, and can be used to differentiate between the two.
Method of assessment
On the sagittal T2W image:
measure the length of the largest fluid-fluid level (A)
measure the maximu...
Fluoroscopic evaluation of oesophagectomy is an important study, given the high rate of complication following oesophagectomy (~10-20% rate of leak). Although the approach will differ slightly depending on the type of oesophagectomy performed, the principles are similar.
Focal areas of signal intensity (FASI), alternatively called focal abnormal signal intensity or unidentified bright objects (UBO), are bright areas on T2-weighted images commonly identified in the basal ganglia (often the globus pallidus), thalamus, brainstem (pons), cerebellum, and subcortical ...
Focussed Assessment with Sonography for Trauma (FAST) scan is a point-of-care ultrasound examination performed at the time of presentation of a trauma patient.
It is invariably performed by a clinician, who should be formally trained, and is considered as an 'extension' of the trauma clinical ...
Follicular monitoring or follicular study is a vital component of in-vitro fertilization (IVF) assessment and timing. It basically employs a simple technique for assessing ovarian follicles at regular intervals and documenting the pathway to ovulation.
Journey to ovulation begins d...
The lateral projection is part of the three view series examining the phalanges, metatarsals and tarsal bones that make up the foot.
The lateral projection additionally examines the talocrural joint.
the patient may be supine or upright depending on comfort
the affected le...
Foot radiographs are commonly performed in Emergency departments, usually after sport-related trauma and often with a clinical request that states lateral border pain. Remember to check the whole film, though. Often, a foot x-ray is also requested for the investigation of osteomyelitis, arthriti...
In breast imaging, forbidden, check or review areas are zones that, according to Tabár, require special attention in mammographic interpretation.
on a mediolateral oblique (MLO) view
the "milky way" (retromammary fat): a 3-4 cm wide band parallel to the edge of the pectoral muscle...
The four chamber cardiac view is an important and routinely performed view in both fetal echocardiography as well as on a standard second trimester anatomy scan.
The four chamber view can only detect some of the congenital cardiac anomalies (~64% according to one study 2) ...
Frontal horn width to intercaudate distance ratio (FH/CC) is used in assessing patients with suspected Huntington's disease.
On the same axial plane obtained on the ACPC (anterior commissure and posterior commissure) line, the ratio between the distance between the caudate heads (where they ar...
Functional endoscopic sinus surgery (FESS) is a type of paranasal sinus surgery performed intranasally using a rigid endoscope. Its primary objective is to restore physiological ventilation and mucociliary transport 1.
Paranasal sinus imaging is crucial in preoperative planning and is also incr...
Fundoplications are forms of antireflux surgery used as a second line of treatment of gastroesophageal reflux disease after failure of medical treatment and first line of treatment of paraesophageal hernia.
A gastric fold is wrapped around the distal esophagus which enforces the lowe...
Many patients, particularly in developing countries, can present late with giant breast masses. They may be single or multiple and either benign or malignant. Many of these conditions are indistinguishable on physical examination alone. Some of these lesions require mastectomy while others can b...
Gissane angle, also known as the "critical angle", is an angular measurement made directly inferior to the lateral process of the talus. It is formed by the downward and upward slopes of the calcaneal superior surface. It is better seen on a lateral plain film of the calcaneus and hindfoot. Its ...
Differentiating a glioblastoma (GBM) from a cerebral metastasis is a frequent challenge, with profound surgical, workup and treatment implications. Unfortunately distinguishing between the two entities is not always straightforward.
This article addresses helpful imaging features to aid in dis...
The global cortical atrophy (GCA) scale, also known as the Pasquier scale, is a qualitative rating system developed to assess cerebral atrophy, especially in the context of neurodegenerative diseases. It evaluates atrophy in 13 brain regions assessed separately in each hemisphere and resulting i...
Ground glass opacification/opacity (GGO) is a descriptive term referring to an area of increased attenuation in the lung on computed tomography (CT) with preserved bronchial and vascular markings. It is a non-specific sign with a wide aetiology including infection, chronic interstitial disease a...
The clinical history will nearly always lead to a short differential or the answer. Show off to the examiner that you have a structured approach to reporting and managing the patient.
uterus: size, version and shape (normal or variant which you should elaborate on and say w...
Haematospermia (less commonly haemospermia) refers to the presence of blood in semen or ejaculatory fluid. It is a symptom that can cause great anxiety in patients despite usually being of benign aetiology.
urogenital infections including sexually transmitted disease
Haematuria in a child is evaluated differently than in an adult in two main respects:
there is a lower likelihood of a malignancy (renal or bladder) causing the haematuria
preference is given to nonionizing radiation
Haematuria can be considered in three main forms:
The haemorrhage exclusion sign can be a useful MRI finding following prostate biopsy.
The normal prostate produces high concentrations of citrate, which among other properties, acts as an anticoagulant 1. As tumour cells are dysfunctional, they will produce lower levels of citrate th...
Haemorrhagic infarct or haemorrhagic transformation of an infarct is seen following breakdown of the lamina of the microvessels.
Intracerebral haemorrhage (ICH) may overlap with a haemorrhagic infarct and hence needs to be differentiated as the line of treatment will vary.
Various types of brain tumours may cause haemorrhage. Increased tumour vascularisation with dilated, thin-walled vessels and tumour necrosis are the most important mechanisms of haemorrhage. The list includes:
choroid plexus carc...
The head and neck cancer therapy response interpretation (Hopkins criteria) is a qualitative system of interpretation for therapy response assessment using PET-CT.
Widely used options for therapy response assessment are clinical examination, histopathology, CT and MR imaging, howev...
LI-RADS (Liver Imaging Reporting and Data System) is both a set of standardised terminology and a classification system for imaging findings in liver lesions. The LI-RADS score for a liver lesion is an indication of its relative risk for hepatocellular carcinoma (HCC). The classification system ...
Hindfoot equinus describes abnormal plantarflexion (calcaneotibial angle >90°) of the foot that occurs in the hindfoot. It occurs in congenital talipes equinovarus and congenital vertical talus.
A hyperechoic liver lesion on ultrasound can arise from a number of entities, both benign and malignant. A benign hepatic haemangioma is the most common entity encountered, but in patients with atypical findings or a risk for malignancy, other entities must be considered.
The approach to HRCT chest in patients with suspected idiopathic interstitial pneumonia (IIP) is with the aim to:
make sure an appropriate study requested i.e. HRCT chest with optimal individually adjusted protocol and ensure adequacy of the HRCT chest quality (see imaging protocol below)
Imaging in liver transplantation is aimed to evaluate donor and recipient for successful transplantation and its outcome.
volume of liver
parenchymal disease (diffuse or focal)
Gunshot injuries often require imaging assessment, and this evaluation has both clinical relevance (assessment of organ damage, surgical planning and prognostication), and often also forensic implications.
Incidence of gunshot injuries to the head is increasing in some countries, ...
Increased retrosternal airspace is an indicator of hyperinflation of the lungs and is usually due to emphysema.
The thickness of the space between the ascending aorta and the posterior margin of the sternum (3 cm inferior to the sternomanubrial joint) and is normally no more than 2.5 cm 1 altho...
It is important to have a systematic way of approaching a case with subfertility in the exam.
Ultrasound is the initial examination of choice. Always say that you would further assess the uterus with 3D ultrasound. You may also say that in my department we would perform a sonohysterogram or HS...
The intermetatarsal (IM) angle refers to the angle measured between the 1st and 2nd metatarsal shaft on an axial view of the foot. In normal situations it is considered to be under 9°. The angle can increase with hallux valgus and metatarsus adductus deformities.
The interseptal distance (ISD) is a measurement used to assess septal area atrophy as a marker for neurodegenerative conditions in patients with memory problems 1.
It is proposed that atrophy of the septal nuclei can commonly be seen in conditions associated with hippocampal atrophy, particular...
Intracranial nonneoplastic cysts are common findings in magnetic resonance (MR) and computed tomographic (CT) brain scans.
Location-based diagnostic approach
A location-based approach is useful in establishing an appropriate diagnosis; some locations are virtually pathognomonic for certain les...
Intradural spinal mass lesions are relatively uncommon, compared to intracranial or extradural masses, and can be challenging to diagnose. Additionally, the need for a pre-operative/non-operative diagnosis is in many ways greater as biopsy of lesions within the cord has the potential of devastat...
The ventricular system of the brain plays host to a variety of unique tumours, as well as tumours that are more frequently seen elsewhere (e.g. meningiomas). Besides, some intra-axial (parenchymal) masses can be mostly exophytic and thus appear mostly intraventricular. A systematic approach taki...
The International Ovarian Tumour Analysis (IOTA) group ultrasound rules for ovarian masses are a simple set of ultrasound findings that classify ovarian masses into benign, malignant or inconclusive masses. These rules apply to masses that are not a classical ovarian mass (e.g. corpus luteum, en...
Isolated free fluid in trauma may or may not represent a significant injury, and this creates a diagnostic dilemma in determining appropriate treatment for these patients.
The presence of isolated free fluid in trauma occurs in 3-5% of blunt trauma patients 1-4.
Isomerism is a term which in general means 'mirror-image'. It is used in the context of heterotaxy and is of two types:
Mirror image of the structures on the left side of the chest along the left-right axis of the body, i.e. patients with isomeri...
This article is dedicated to the humble joint effusion, particularly the plain radiographic appearances.
A joint effusion is defined as an increased amount of fluid within the synovial compartment of a joint. There is normally only a small physiological amount of fluid. Abnormal fluid accumulat...
Left upper lobe collapse has distinctive features but can be challenging to identify on chest radiographs by the uninitiated.
For a general discussion refer to the article on lobar collapse.
The left upper lobe collapses anteriorly becoming a thin sheet...
Getting a film with left upper lobe collapse in the exam is one of the many exam set-pieces that can be prepared for.
This frontal chest radiograph shows a hazy (or veil-like*) opacification of the left hemithorax that is associated with superior displacement left hilum and horizon...
Lines and tubes are important components in chest radiographic evaluation.
Nasogastric (NG) tube
See: nasogastric tube positioning.
NG tube tip ≥10 cm distal to the gastro-oesophageal junction
i.e. below the left hemidiaphragm
insertion into trachea or bron...
This is a basic article for medical students and other non-radiologists
Lobar collapse is relatively common and occurs following obstruction of a bronchus. Gas is resorbed from the lung parenchyma distal to the obstruction resulting in the collapse of the lung, with volume reduction and negativ...
The parotid gland consists of a superficial and deep lobe. Determining the location and extent of the lesions affecting the gland is an essential aspect of imaging and vital information which needs to be conveyed to the surgeon.
Method of evaluation
The following lines are proposed for differe...
The lower zone is one of the four chest radiograph zones.
on frontal chest radiographs, extends inferiorly from the inferior aspect of the hilum to the hemidiaphragm
Low grade osteosarcoma is an uncommon subtype of osteosarcoma accounting less than 1% of all osteosarcomas.
Low grade osteosarcoma affects individuals of higher age group as compare to the other subtypes of osteosarcoma. The usual age of presentation is 19 to 54 years with the mea...
The IASLC (International Association for the Study of Lung Cancer) 8th edition lung cancer staging system was introduced in 2016 and supersedes the IASLC 7th edition.
It is as follows:
T: primary tumour
Tx: primary tumour cannot be assessed or tumour proven by the presence of mal...
Lymph node imaging has become an important task for the radiologist in present days, aiding the clinician in determining whether they are benign or malignant. Multiple modalities are being used for the assessment and characterization of lymph nodes, each with its advantages and drawbacks.
Magnetic resonance neurography (MRN) is a relatively new non-invasive imaging technique for dedicated assessment of peripheral spinal nerves.
It is used to assess peripheral nerve entrapments and impingements as well as localization and grading of nerve injuries and lesions.
Malignant ovarian lesions can have typical sonographic features, and thus ultrasound is the imaging of choice for initial evaluation of suspected ovarian neoplasm.
The features of malignant ovarian neoplasm on ultrasonography include:
mass >10 cm with locul...
Mammography is a dedicated radiographic technique for imaging the breast.
Types of mammography
In general terms, there are two types of mammography: screening and diagnostic.
Mammography differs significantly in many respects from the rest of diagnostic imaging.
The management of incidental adrenal masses revised in 2017 by the Adrenal Subcommittee of the Incidental Findings Committee of the American College of Radiology is an algorithm for the management of patients who are:
adults (i.e. 18-year-old or over)
asymptomatic for adrenal pathology
The McGill Thyroid Nodule Score (MTNS) is a scoring system developed to estimate the risk of malignancy of thyroid nodules.1
The MTNS is based on 22 parameters:
eight clinical or laboratory parameters
gender (male): 1 point
age (>45 years old): 1 point
palpable nodule (prese...